Anode



Patented June 9, 1936 PATENT 'OFFICE ANODE John L. Young, Pittsb'gh,Pa., assignor to National Radiato' Corporation, a corporation ofMaryland Application November 1, 1934, Serial No. !50,929 2 Claims. (l.Zoi-4) This invention relates to electrolytic cells for the deposit ofmetals. I have developed it in making deposit of iron, and in thatparticular application I shall describe it. I

In the accompanying drawing Fig. I is a diagrammatic view in section ofan anode of my present invention in one of its practicable forms; Fig.II is a view' in section of a portion of the walls of an electrolyticcell, and of the anode of my invention in another permissible form; andFigs. III, IV, and V are views in elevation of the anode of theinvention in yet other forms.

It has heretofore been proposed to make electrolytic deposit of ironfrom a solution of a ferrous salt, typically ferrous ammonium sulphate,as an electrolyte, using an iron anode; but the proposal has beenattended with practical difliculties not heretofore successfullyovercome. As the operation progresses the electrolyte tends to .becomeincreasingly acid in character, with the conversion of the dissolvedferrous ammonium sulphate to ferric salt, and the iron deposit upon thecathode tends to become so brittle as to be useless. The proposal hasbeen made to correct 25 this tendency by maintaining iron sponge insuspension in the electrolyte; but the proposal leads to otherdifficulties. The bulk of the sponge iron is lost in an undeslredprecipitate of ferrous hydroxide, and the deposit on the cathode tendsto become rough, and in that respect of impaired utility. And it has not'been found practically possible so to maintain the pH value of the bathwithin the limited range essential to practical success. V

I have discovered that if iron sponge be employed, not as a substanceSuspended in and distributed through the body of electrolyte, but as theanode itself, the pH value of the electrolyte may be maintained withinthe requisite range, and a successful and practical deposit obtained.

While I do not wish to limit my invention by theoretical considerations,I have reason to believe that my practical success, in contrast to the 4impracticability of prior proposals, is due to the fact that, whereasthe substance of the iron anode as heretofore employed has beenaccessible to the electrolyte over surface areas that were smallrelatively to the mass of metal consumed, with -an anode of iron spongethe substance of the anode is accessible over surface areas that arelarge relatively to the mass consumed. I, therefore, find the essentialcharacter of the anode of my invention to be the flnely dividedcondition of the iron of which it is constituted.

There are various ways in which the anode may be formed, to possess thecharacteristic that it shall consist essentially of iron in finelydivided condition. In one embodiment of the invention a supporting coreof magnetic character may carry, magnetically Secured, a surface coatingof flnely divided iron, and in such case, as in the progress of theelectrolytic operation, it is consumed, the coating may be renewed andbuilt up again by sprinkling fresh supplies of nely divided iron intothe electrolyte. such material so sprinkled in will at once be attractedmagnetically -to and will constitute renewal of the coating upon thecore. The core may be permanently magnetic, or it may be renderedmagnetic by means of an electric current. In Fig.' I an anode is shown,consisting of a core i and a coating! of flnely divided iron, and it maybe 4 understood that the core is magnetized, and that the coating isheld magnetically to it.

Again, advantage may be taken of the fact that certain metals in moltenstate have the characteristic of wetting iron, in order to form an anodeof the character indicated. This is illustrated in Fig. II. A body 3 ofmercury, for example, suitably disposed within the cell 4 (spread as abath upon the bottom of the cell) may carry a skim or coating 5 offlnely divided iron sprinkled upon it. And in this case also the coatingmay be renewed by sprinkling fresh supplies of finely divided iron intothe. cell, while the operation is in progress; for the sprinkled-in ironwill sink through the electrolyte and rest upon the surface of'the bathof mercury.

I have found that iron sponge compressed sufficiently to form a coherentmass of permanent shape will still retain its finely divided characterto sumcient extent, and will be found effective in the electrolyticoperation. Accordingly, another way of 'forming a practicable electrodeis to compress iron sponge to suitable shape and size and to mount thecompressed body or bodies (for, conveniently, a plurality of smallerunits will thus be built together) upon a carrier that is at once aconductor and is more inert than is the body of compressed sponge to thecorrosive action of the electrolyte. In Flg. III a plurality of discs orblocks G are shown, which may be understood to be bodies of iron spongecompressed sufllciently to give coherence, but not sufliciently todestroy the characteristic of flnely divided material, large surfacearea relatively to mass. These bodies 6 are shown to be combinedandformed into a unitary anode structure by means of strips 'I and 8 ofanother metal or alloy cast in situ upon them and establishingelectrical continuity. These uniting strips are formed of a metal oralloy that is inert to the corrosive action of the electrolyte, orsubstantially so. They are inert, relatively to the bodies of ironsponge, both by virtue of the material of which they are composed and byvirtue of the condition of the material: while the bodies 6 are ofspongy condition, the strips 'l and 8 are dense. Although it is notrequisite, it is advantageous that the metal or alloy of which thestrips 1 and 8 are formed be such as to possess when in moiten statethe' characteristic of wetting iron. such a metal is lead. In operationthe strips of relatively inert metal or alioy persist, whilethe'compressed iron sponge is gradually eaten away by the corrosiveaction of electrolysis. In the use of the anode in this embodiment,manifestly, there must be replacement of the worn anode.

` Again, the iron sponge may be compressed upon a supporting grid orcarrier of another metal, the

compression being sufficient to efl'ect mechanical union and integrationand electrical continuit'y, but insuflicient to destroy thecharacteristic advantage of iron sponge described above. illustrated inFig. IV, in which in dotted lines a body 9 of iron sponge is shown to beshaped'- and compressed upon a grid o, 'that may be understood to beformed of denser iron.

The ,iron sponge may be given coherence by compression within a thincylinder of a metal This is l2 that may be understood to be a body ofcompressed iron sponge. Within the body !2, in turn, is incorporated asupporting and electrically conducting carrier I 3.

Proceeding with an anode of finly divided iron, the electroiyte will asoperation progresses be found to have a relatively constant pH value;the pH value will be found to range from 6 to '7. And within that rangeelectrolysis progresses successfully and the deposit is such incharacter as to be useful. A deposited sheet, for example, may besuccessfully removed from a stripping cathode, and brought by annealingto serviceable condition. e

I claim as my invention:

1. A soluble anode for' metallic electro-deposition 'consisting of nelydivided metal resting upon the surface of a supporting body of anothermetal in liquid state.

2. An anode for an electrolytic cell consisting of finely divided ironheld magnetically upon the surface of a supportingbody of magneticcharacter.

J OI-IN L. YOUNG.

